1 #include<iostream>
2 #include<cstdio>
3 #include<cstdlib>
4 #include<cstring>
5 #include<string>
6 #include<queue>
7 #include<algorithm>
8 #include<map>
9 #include<iomanip>
10 #include<climits>
11 #include<cmath>
12 #include<stdlib.h>
13 #include<vector>
14 #include<stack>
15 #include<set>
16 #define INF 2000000000
17 #define MAXN 110
18 #define maxn 1000010
19 #define Mod 1000007
20 #define N 1010
21 using namespace std;
22 typedef long long LL;
23
24 int n, m;
25 bool G[MAXN][MAXN];
26 int u, v;
27
28 void Floyd()
29 {
30 for (int k = 1; k <= n; ++k)
31 for (int i = 1; i <= n; ++i)
32 for (int j = 1; j <= n; ++j)
33 G[i][j] |= G[i][k] & G[k][j];
34 }
35
36 int main()
37 {
38 while (~scanf("%d%d", &n, &m), n + m) {
39 memset(G,0,sizeof(G));
40 for (int i = 0; i < m; ++i) {
41 scanf("%d%d", &u, &v);
42 G[u][v] = true;
43 }
44 Floyd();
45 int sum,ans = 0;
46 for (int i = 1; i <= n; ++i) {
47 sum = 0;
48 for (int j = 1; j <= n; ++j) {
49 if (G[i][j] || G[j][i]) sum++;
50 }
51 if (sum == n - 1) ans++;
52 }
53 cout << ans << endl;
54 }
55 return 0;
56 }
